Conduct disorder is one of the most common and important clinical disorders in children, and continuing efforts are being made to improve diagnostic criteria for and subtyping of conduct disorder. Neurobiological markers, including conditioning deficits, could in theory bring objective information to the diagnostic process and help differentiate the life-course persistent subtype of conduct disordered individuals from more transitory antisocial children. The long term goal of this pilot study is to lay the foundations fo a future prospective longitudinal study of conduct disorder in childhood and adolescence which can provide new insight into continuity and change throughout this important developmental period, with potential implications for diagnosis and treatment. The central hypotheses, based on both the prior literature and the applicant's recent findings, are that children with conduct problems at both ages 8 and 9 are characterized by reduced conditioning to punishments and enhanced conditioning to rewards, and that children with both conditioning deficits and adverse home environments show more conduct problems. Hypotheses will be tested by pursuing three specific aims: 1) to determine the relationships between conduct problems and conditioning to both rewards and punishments, 2) to determine the stability and change in conduct problems and the specificity of conditioning measures to the early-onset persistently antisocial group, and 3) to determine whether conditioning deficits interact with psychosocial adversity in predisposing to conduct problems. This pilot study plans to assess conduct disorder symptoms, autonomic conditioning, and social adversity in a community sample of 340 8-year-old boys and girls in the area of Brooklyn, New York, and also in a one-year follow-up at age 9 years. Electrodermal and cardiovascular activity will be assessed during appetitive and aversive conditioning tasks. The research proposal is innovative because: (1) for the first time it examines associations between conduct problems and the balance of appetitive conditioning and aversive conditioning in children, (2) it uses a prospective longitudinal design, and (3) it investigates the interaction between conditioning deficits and psychosocial factors in predisposing to conduct problems. NIH support of this proposal will provide the applicant with the experience necessary to transition into an independent investigator. More importantly, identification of early biomarkers such as conditioning deficits, along with the role of psychosocial factors, may increase insight into the underlying psychopathological processes involved in the development of conduct problems. Programmatically this knowledge has potential implications for clinical diagnosis and behavioral modification treatment programs, and may help to target treatment efforts on those children in most need.